JP5319551B2 - Especially pressure tanks such as hydraulic accumulators - Google Patents

Abstract

A pressure tank, in particular hydraulic accumulator (3, 5), has a parting element (1) separating a space (11) for a first gaseous working medium from a space for a second fluid working medium in the tank. The parting element is flexible, can move under deformation and defines a domed main parting plane extending from an annular edge (13). The parting element (1) is produced from a substance having a fluoroplastic material, preferably a substance composed entirely of fluoroplastic material.

Description

  The invention is movable while deforming, separating the space in the tank for the first medium, in particular a gaseous working medium, from the space for the second working medium, in particular a fluid, and annular More particularly, the invention relates to a pressure tank, such as a hydraulic accumulator, having an elastic separation element that defines a dome-shaped main separation surface extending from the edge.

  Such a pressure tank in the form of a hydraulic accumulator is disclosed in US Pat. Elastic separation element made of rubber-like material (synthetic rubber such as acrylonitrile butadiene rubber) can be moved while deforming with known hydraulic accumulators, forming a membrane that separates the gas side from the fluid side in the accumulator housing To do. Two main requirements must be imposed on the operating behavior of a hydraulic accumulator with such a membrane that can be deformed and moved. On the one hand, the membrane impermeability must be guaranteed to prevent gas diffusion. On the other hand, the corresponding mechanical properties of the film that are maintained even under the influence of corrosive media are required, in particular ease of movement and repeated bending strength.

German Patent No. 2852912

  In the known hydraulic accumulator described above, these requirements are only partially met. In order to improve the impermeability of the rubbery membrane, known accumulators have an annular bead-like ridge that projects from the main separation surface in a continuous and continuous manner. As the average density of the wall is increased by the ridges, diffusion impermeability is actually increased, but the wall thickness is greatly increased, so that the wall is significantly hardened and thus less mobile.

  The object of the present invention is to make available a pressure tank, in particular a hydraulic accumulator, characterized by a much improved operating behavior compared to this prior art.

  According to the invention, this object is achieved by a pressure tank having the features of claim 1 as a whole.

  That is, according to the invention, in the pressure tank, there is a separation element that has a fluoroplastic material or preferably is made entirely of a material made of a fluoroplastic material, while having excellent diffusion impermeability. On the other hand, a separation element is provided that has optimum mechanical properties for use as a membrane in a hydraulic accumulator, such as extremely good repeated bending strength. Thus, very small wall thicknesses can be used. For this reason, desirable ease of movement of the film can be obtained. Based on the resulting good response behavior, the pressure tank is particularly suitable for use as a pulsation damper.

  Polytetrafluoroethylene has been found to be a particularly suitable material.

  Since polytetrafluoroethylene (PTFE) cannot be plastic molded due to its very high melt viscosity, the desired moldings made from this material are pressed from powder raw material at 200-400 bar and 370-380 without pressure. Sinter at °. When it is necessary to obtain a membrane, it is generally peeled from the cylindrical block. Therefore, polytetrafluoroethylene is generally marketed in the form of rigid solid bodies such as slabs, rods, tubes and the like. Those skilled in the membrane art are surprised to nevertheless be able to obtain separation elements that are made entirely or partially from polytetrafluoroethylene material and can even perform the function of a flexible rolling membrane. .

  Furthermore, since the PTFE material has a particularly good chemical resistance, the pressure tank according to the invention is also suitable for use in the presence of a chemically corrosive medium.

  In an advantageous embodiment, the separating element defines a main dome-shaped separating surface with an annular bead-like ridge protruding on the side that is inward of the dome. By using the dome-shaped membrane in this manner, a relatively large change in the volume of the adjacent working space in the pressure tank can be caused because the deformation is easy in the pressure tank.

  In a preferred embodiment, the successive ridges are separated from each other by flat wall portions extending along the main separation surface. Therefore, there is one free space between adjacent ridges, which can be used for relative movement of the adjacent ridges, so there is no annular bead that supports each other and reinforces the structure adjacent to each other However, the separation element can be transformed as a rolling membrane.

  Preferably, the top of the annular bead-like ridge has a rounded dome so that the notch effect is avoided.

  In a particularly advantageous embodiment, the annular bead-like ridge is formed by a fold that opens outward and forms an annular groove-like depression in the main separation surface. Depending on the height of the fold, the membrane thus formed can use a particularly large length of material strip that can be moved to roll up and pull out the membrane, as in the case of bellows.

  Preferably, in this case, the height of at least one fold, measured along its vertical axis from the open end to the top of the fold is arranged to be different from the height of the other folds.

  As has already been found, particularly good mechanical properties are obtained when the first bend closest to the annular edge has a smaller height than other adjacent bends.

  Also, at this point, the wall portion extending from the annular edge to the nearest first bent portion has the maximum value at the annular edge, and the wall portion between the bent portions toward the first bent portion. It is advantageous to have a wall thickness that decreases to the value of the wall thickness. By forming the edge thickness in this way, the membrane is clamped on the corresponding housing element of the pressure tank and the sealing connection of the clamping site without adversely affecting the elasticity of the rest of the membrane The formation of is promoted.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

Fig. 2 shows a slightly schematic longitudinal section of an exemplary embodiment of a pressure tank according to the invention in the form of a hydraulic accumulator, showing only the lower region of the housing and the upper boundary of the housing. FIG. 2 shows a longitudinal cross-sectional view enlarging a half of its side compared to FIG. 1, showing only the separating element of the exemplary embodiment of FIG. 1 manufactured as a rolling membrane. FIG. 3 shows a partial view of the region identified by circle III in FIG. 2, further enlarged compared to FIG.

  Of the exemplary embodiment of the pressure tank according to the invention in the form of a hydraulic accumulator, FIG. 1 shows a lower part 3 of the housing having a lower fluid connection 9 coaxial with the longitudinal axis 7 of the housing, and a lower part 3 of the housing. Only the top 5 piece of the adjacent housing is shown. At the connection site between the lower part 3 of the housing and the upper part 5 of the housing, the open annular edge 13 of the separating element in the form of a rolling membrane, indicated generally as 1, is tightly clamped. Here, the thickened edge 21 of the rolling membrane is supported on the annular surface 22 of the lower part 3 of the housing on the one hand and adjacent to the O-ring 15 on the other hand, the O-ring 15 being the axis of the upper part 5 of the housing. It is placed in an annular groove 20 on the annular body 14 projecting in the direction.

  1 and 2 show the roll membrane 1 in a fully unfolded or elongated state, in which the space 11 located above the membrane 1 in FIG. 1, ie the gas side of the hydraulic accumulator has the largest volume. Since there is no fluid pressure at the fluid connection 9, the membrane 1 is in contact with the inner wall of the lower part 3 of the housing, and the center reinforcing bead 29 of the membrane 1 overlaps the edge of the fluid connection 9. Forms a mechanical protective means that prevents the membrane 1 from being pressed against the fluid connection 9 when not present.

  2 and 3 illustrate further details of a rolling membrane 1 made from PTFE material. Since PTFE material has very good diffusion impermeability and particularly good strength properties, the wall thickness of the membrane required by the rolling membrane 1 outside the annular edge 13 is very small, which makes the dome-shaped main separation surface Define. Although the continuous annular bead-like ridges project inwardly from this main separation surface, in the example shown, they are not by solid form beads, but the first bend closest to the edge 13 is 17. The other bent portions shown by and adjacent to each other are formed by the bent portions shown by 19 respectively. As can be seen from FIG. 1, the wall thickness decreases from the thickened wall 21 at the annular edge 13 to the first bend 17 and is a flat wall located between the bends 17 and 19, respectively. It changes so that it may become the value of the thickness of the part 23. FIG. In an actual embodiment, the wall thickness decreases from a value of 1.2 mm to a value of 0.5 mm from the thickened part 21 to the first curved part 17, which is 0.5 mm. 19 is the value indicated by the continuous wall portion 23 between 19. As FIG. 2 similarly shows, the inner thickened edge 21 forms a kind of shell shape that forms a partial enclosure of the O-ring 15 not shown in FIG.

  As can be seen from FIG. 2 as well, when measured along the vertical axis 25, the height of the first bent portion 17 is smaller than the continuous bent portions 19 each having the same height, and all the bent portions 17 and The top of 19 is dome-shaped. Since the folds 17 and 19 are open on the outer side of the dome, an annular groove-like depression 27 (see in particular FIG. 3) is formed, each of which is between the wall portions 23 of the dome of the main separating surface. Form a break in the middle. As can be seen in particular in FIG. 3, the inner width of the annular groove-like depression 27 at the open ends of the bent portions 17, 19 is much smaller than the height of the bent portion measured along the vertical axis 25, in this example The height of the bent portion 19 is about four times the inner width.

  As is also apparent from FIG. 3, the inner surface of the depressions 27 of the bent portions 17 and 19 extend while slightly extending toward the open end, so that the open end of the depression 27 is the top of the bent portion. It has a width greater than the bottom of the recess 27 in the region. As shown in FIG. 2, each of the vertical axes 25 of the bent portion 19 is oriented substantially perpendicular to the tangential plane of the adjacent wall portion 23, while the vertical axis 25 of the first bent portion 17. Extends slightly inclined with respect to this tangential plane, and the vertical axis 25 of the first bend 17 is at an angle of about 10 ° with respect to the plane of the annular edge 13. With respect to the continuous bent portions 19 arranged from the top to the bottom, the vertical axis 25 is gradually inclined with respect to the plane of the edge 13.

  In this example, the annular bead-like bulge projecting inside the membrane 1 is formed by the curved portions 17 and 19, so that particularly easy mobility is obtained when the membrane is rolled up. However, it is also possible to manufacture an annular bead-like ridge as a solid body. Unfilled PTFE can be used and may involve fillers and / or combinations of fillers conventionally available for PTFE materials, for example where particularly high heat resistance or other special properties are desired. . In particular, glass fiber materials, carbon or metal fillers are conceivable.

  Semi-finished PTFE materials are available in many forms, such as membranes peeled from blocks, solid bars, circular blanks, and the like. Based on the mechanical properties, a finished product such as a rolling membrane used in the pressure tank according to the invention can be produced by cutting the powder raw material from a pressed and sintered compact. However, particularly thin-walled articles can be formed by blow molding a PTFE diffusion prior to sintering. If the spherical membrane shape shown in FIG. 1 is obtained from the solid body of polytetrafluoroethylene, then a separation membrane having the shape illustrated by cutting a raw object is obtained. In order to minimize the pieces of polytetrafluoroethylene formed during the cutting process, a hemispherical pre-formed object may preferably be produced as a blank during molding.

The polytetrafluoroethylene material described above as the fluoroplastic material may comprise both pure PTFE and modified PTFE, and may comprise both unfilled PTFE and PTFE compounds. In the case of modified PTFE materials, fillers such as bronze, carbon dust, MoS ₂ , and glass and carbon fiber materials are possible. In addition to PTFE, other fluoroplastic materials include ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene copolymer (ECTFE), polychlorotrifluoroethylene copolymer (PCTFE), perfluoroalkoxy copolymer. (PFA), polyvinylidene fluoride (PVDF) and tetrafluoroethylene perfluoropropylene (FEP) can be used.

Claims (11)

The space (11) in the tank for the first medium, which is movable while being deformed and in particular a gaseous working medium, is separated from the space for the second working medium, in particular a fluid, and is annular In a pressure tank, in particular a hydraulic accumulator (3, 5), having an elastic separating element (1) defining a dome-shaped main separating surface extending from the edge (13)
It said elastic separating element (1) has a fluorine plastic material, Ri Do from the preferred overall the fluorine plastics material,
An annular bead-like ridge (17, 19) in the form of a continuous bend projects from the side of the elastic separating element, whose vertical axis (25) extends from the annular edge (13) to the elastic separating element ( 1) A pressure tank, which is gradually inclined with respect to the plane of the annular edge (13) toward the bottom of 1) . 2. The elastic separating element (1) defines a dome-shaped main separating surface, and an annular bead-like ridge (17, 19) projects on a side that is inward of the dome. As described in the pressure tank. 3. The continuous annular bead-like ridges (17, 19) are separated from each other by a flat wall portion (23) extending along the dome-shaped main separating surface. The described pressure tank.   4. Pressure tank according to claim 2 or 3, characterized in that it has a dome with rounded tops of the annular bead-like ridges (17, 19). The annular bead-like ridge is formed by a curved part (17, 19) that opens outward and forms an annular groove-like depression (27) in the dome-shaped main separating surface. pressure tank according to any one of 4.   The height of at least one fold (17) measured along its vertical axis (25) from the open end to the top of the fold (17, 19) is the height of the other fold (19). The pressure tank according to claim 5, wherein the pressure tank is different. And having the other folds (19) is smaller than the height the annular edge (13) nearest the first fold portion is (17) adjacent the pressure tank according to claim 6 .   The height of the bends (17, 19) is at least twice as large as the width of the formed annular groove (27) measured at the open end of the bends (17, 19). The pressure tank according to claim 6 or 7, characterized in that.   9. A pressure tank according to any one of claims 6 to 8, characterized in that the vertical axes (25) of the continuous folds (17, 19) are inclined by a small angle with respect to each other.   10. The flat wall portion (23) extending between successive folds (17, 19) each having the same wall thickness. Pressure tank.   The wall portion extending from the annular edge (13) to the nearest first curve (17) has a maximum value on the annular edge (13), and the first curve ( 10. Pressure tank according to claim 9, characterized in that it has a wall thickness that decreases towards the value of the wall thickness of the wall part (23) between the bends (17, 19) towards 17).

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